Optical guidance is a widely used technique for guiding and navigating remote and typically blind, vehicle platforms towards a target destination.
For example, GB1315351 discloses a method of determining the co-ordinates which an object has in a cross-section of a beam of EM radiation in relation to the axis of the beam. The method is applicable to the control of a flying object being steered along a guiding beam. The beam is produced and transmitted in such a way that any cross-section thereof normal to its axis is an identical projection of the same transmitted image, each component of which provides measurement data corresponding to the coordinates of that component relative to the beam axis. Thus, the co-ordinates of the object in the beam can be evaluated by the object itself from the data. A modulation disc rotating in front of a radiation source produces the image to be projected, components of the image corresponding to values of modulation of the beam and providing the data. In the apparatus for performing the method, a projector forms a radiation source for image projection. The radiation is bunched and projects the modulation disc, as an image. An optical mirror system projects the image in such a way that each cross-section of the beam contains an identical image. The modulation disc may be circular with transparent slots and opaque webs. If the flying body deviates from the beam axis, the measurement data in the image components are used to provide control signals which are fed to the steering gear of the body. The optical image projection system may contain infra-red filters to allow steering of the body by infra-red. To prevent the flying body from deviating further from the beam axis as it moves away from the launch site, the bunching of the radiation is varied. The invention may also be applied to assist the landing of an aircraft when the latter is steered along the beam axis to the landing strip.
U.S. Pat. No. 4,096,380 discloses a system for transmitting light signals between a missile and a missile control launching site by utilizing a laser beam light signal transmission path. The system comprises a laser emitter having a relatively broad transmission beam for producing a transmission path for the modulated light signals during the flight of the missile. The system obviates the need for light transmission lines or other physical connection between the missile and the control station and provides for continuously aiming the laser beam on the missile by means of a follow-up device responsive to a portion of the beam reflected from the missile. At least one crown of triple mirror reflectors is distributed about the axis of the missile to enable the missile to reflect the laser beam impinging thereon independently of the flight position of the missile. The laser beam is modulated to transmit control light signals from the control station and information light signals from the missile.
U.S. Pat. No. 4,243,187 discloses a line of sight guidance system in which the radiated output of a pulsed laser is spatially modulated to produce a beam radiated from an optical projector along a first axis, including a missile or projectile carrying a beam receiver and signal decoder which receives and decodes information in the beam to enable the missile to seek a beam center, with an apparatus for generating a lead angle axis reference for the missile. The basic technique comprises FM modulating the rotational rate of an orbitally driven projected beam chopping spoked reticle. The FM modulation amplitude is chosen to equal the magnitude of the desired angular change of the projected spatially coded axis, while the FM modulation phase is made to equal the direction in which the projected spatially coded axis is shifted. The receiver at the missile interprets the image of the reticle pattern as if the receiver were displaced from the un-modulated first axis position in a direction from the beam center as indicated by the modulation phase. Since the missile is controlled to the beam axis center, it follows the coded axis shift.
U.S. Pat. No. 5,560,567 discloses a method and apparatus for passive tracking and guidance in missile systems. The system is utilized in conjunction with a target acquisition system such as a scanning infrared detection system. The target and missile are sensed and the measured displacement there between is utilized in conjunction with calculated nominal trajectory data to generate guidance control signals. In a preferred embodiment of the present invention, the guidance control signals are transmitted to a receiver on the missile utilizing a radar frequency transmitter.
U.S. Pat. No. 5,533,692 discloses a beam of electromagnetic radiation which is spatially encoded using a digital phase modulation technique. The spatial encoding defines the beam cross section into a series of resolution elements each identified by a different digital code. The codes defining resolution elements are detectable by a missile located in the radiation beam and can be used to define the location of the missile in this beam. In the preferred embodiment, an encoding mask, moved through the beam at its source, provides digital phase modulation. The mask is provided with a series of bit areas, each of which bears at least two sets of cyclically recurring bands effective to modulate a detectable parameter of the radiation, such as intensity. The spacing between adjacent bands of a set, termed a bit cycle, is proportional to a predetermined phase of the modulation of the beam parameter. The novel arrangement enables the missile to identify its position within the beam under conditions of severe atmospheric turbulence and object induced perturbations to provide corrective maneuvers for maintaining the missile velocity vector aligned with the beam.